Environment dependent photophysical and fluorescence turn-off sensing properties of Fe(iii) by substituted phenyl isochromenopyrrol-5-ones.

Analogues of isochromenopyrrolone were synthesized using Montomorillonite K10 as a catalyst and characterized. The electronic structure and geometry of all the synthesized compounds were investigated experimentally by UV-visible absorption and fluorescence spectroscopy. A negligible shift was observed in the absorption spectrum while a large red shift was observed in the fluorescence spectrum upon changing from non-polar to polar solvents. The experimental results were compared with those from density functional theory calculations. The observed photophysical properties were induced from the solvent environment. Except for chlorosubstituition, other functional groups like methyl, dimethyl, diethyl or methoxy, did not influence the electronic properties of the molecules significantly. The experimental results were in good agreement with the theoretical interpretations. Moreover, these isochromenopyrrolones possess excellent sensing ability for Fe(iii) ions via the fluorescence turn-off mechanism with a detection limit of ∼10-6 M and an association constant of ∼103 M-1. It is proposed that these molecules can find their use in environment sensing applications.